I don't remember exactly how old she was, but we were in our last years of university (I failed out, she graduated) so she was definitely in her early twenties, 22-24, somewhere in there.

And, yeah, no, my amateur and as such meaningless guess of a diagnosis was also that part of the delusion was a need to feel special. She talked about how most other people didn't know the truth, they couldn't know the truth, because she had magic power that let her know things about the world that normal humans couldn't. You get that sort of language in conspiracy theorists and other types of people who want to feel special, they want to be in on some secret that everyone else can't be. So I'd say that's definitely part of it. But I also think, especially with her believing in a third parent when she was initially abandoned by her father and effectively abandoned by her mother until her father got custody of her again, I think most of it stems from her trauma as a child. Even that need to feel special, with no real parental figure for many of her formative years (I don't remember how old she said she was when her father regained custody of her), probably stemmed from that lack of anyone encouraging her.

But, ultimately, I don't know. She didn't tell me half of this stuff until we were breaking up. And I'm not a psychologist, and she very much needed one.